Salicylaldoxime

Salicylaldoxime
Names
	IUPAC name Salicylaldehyde oxime
	Other names Saldox; 2-[(E)-(hydroxyimino)methyl]phenol
Identifiers
CAS Number	94-67-7 ;
3D model (JSmol)	Interactive image;
ChemSpider	10446269 ;
ECHA InfoCard	100.002.140
PubChem CID	5359280;
UNII	2QTV2A0T5Q ;
CompTox Dashboard (EPA)	DTXSID9052638 ;
	InChI InChI=1S/C7H7NO2/c9-7-4-2-1-3-6(7)5-8-10/h1-5,9-10H/b8-5- Key: ORIHZIZPTZTNCU-YVMONPNESA-N ; InChI=1/C7H7NO2/c9-7-4-2-1-3-6(7)5-8-10/h1-5,9-10H/b8-5- Key: ORIHZIZPTZTNCU-YVMONPNEBT;
	SMILES Oc1ccccc1/C=N\O;
Properties
Chemical formula	C7H7NO2
Molar mass	137.138 g·mol−1
Appearance	white to off-white crystals
Melting point	59 to 61 °C (138 to 142 °F; 332 to 334 K)
Solubility in water	25 g L−1
Hazards
NFPA 704 (fire diamond)	2 1 0
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Salicylaldoxime is an organic compound described by the formula C₆H₄CH=NOH-2-OH. It is the oxime of salicylaldehyde. This crystalline, colorless solid is a chelator and sometimes used in the analysis of samples containing transition metal ions, with which it often forms brightly coloured coordination complexes.^[1]

Reactions

Salicylaldoxime is the conjugate acid of a bidentate ligand:

2 C₆H₄CH=NOH-2-OH + Cu²⁺ → Cu(C₆H₄CH=NOH-2-O)₂ + 2 H⁺

In highly acidic media, the ligand protonates, and the metal aquo complex and aldoxime are liberated. In this way the ligand is used as a recyclable extractant. It typically forms charge-neutral complexes with divalent metal ions.

Analytical chemistry

Structure of the copper(II) complex of the conjugate base of salicylaldoxime. The hydroxyl groups form hydrogen bonds to the phenolate oxygens.

In the era when metals were analysed by spectrophotometry, many chelating ligands were developed that selectively formed brightly coloured complexes with particular metal ions. This methodology has been eclipsed with the introduction of inductively coupled plasma methodology. Salicylaldoxime can be used to selectively precipitate metal ions for gravimetric determination. It forms a greenish-yellow precipitate with copper at a pH of 2.6 in the presence of acetic acid. Under these conditions, this is the only metal that precipitates; at pH 3.3, nickel also precipitates. Iron (III) will interfere. ^[2] It has been used as an ionophore in ion selective electrodes, with good response to Pb²⁺ and Ni²⁺.^[3]

Extraction of metals

Saloximes are used in the extraction and separation of metals from their ores. In one application of hydrometallurgy, Cu²⁺ is extracted into organic solvents as its saloxime complex.^[4]

References

^ Smith, Andrew G.; Tasker, Peter A.; White, David J. "The structures of phenolic oximes and their complexes" Coordination Chemistry Reviews 2003, volume24, pp. 61-85. doi:10.1016/S0010-8545(02)00310-7
^ SH Simonsen; HM Burnett (1955). "Spectrophotometric Determination Of Copper With Salicylaldoxime - Application To Analysis Of Aluminum Alloys". Analytical Chemistry. 27 (8): 1336–1339. doi:10.1021/ac60104a039.
^ EK Quagraine; VPY Gadzekpo (December 1992). "Studies Of Spectrophotometric Reagents In Some Transition-Metal And Lead Ion-Selective Electrodes". Analyst. 117 (12): 1899–1903. Bibcode:1992Ana...117.1899Q. doi:10.1039/an9921701899.
^ Tasker, Peter A.; Tong, Christine C.; Westra, Arjan N. (2007). "Co-extraction of Cations and Anions in Base Metal Recovery". Coordination Chemistry Reviews. 251 (13–14): 1868–1877. doi:10.1016/j.ccr.2007.03.014.

External links

Chemical data at NIST Chemistry WebBook

[1] Smith, Andrew G.; Tasker, Peter A.; White, David J. "The structures of phenolic oximes and their complexes" Coordination Chemistry Reviews 2003, volume24, pp. 61-85. doi:10.1016/S0010-8545(02)00310-7

[2] SH Simonsen; HM Burnett (1955). "Spectrophotometric Determination Of Copper With Salicylaldoxime - Application To Analysis Of Aluminum Alloys". Analytical Chemistry. 27 (8): 1336–1339. doi:10.1021/ac60104a039.

[3] EK Quagraine; VPY Gadzekpo (December 1992). "Studies Of Spectrophotometric Reagents In Some Transition-Metal And Lead Ion-Selective Electrodes". Analyst. 117 (12): 1899–1903. Bibcode:1992Ana...117.1899Q. doi:10.1039/an9921701899.

[4] Tasker, Peter A.; Tong, Christine C.; Westra, Arjan N. (2007). "Co-extraction of Cations and Anions in Base Metal Recovery". Coordination Chemistry Reviews. 251 (13–14): 1868–1877. doi:10.1016/j.ccr.2007.03.014.

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